1. Field of the Invention
The present invention relates to a device for positioning submarine pipeline robots and method thereof, which belongs to the technical field of pipeline detection.
2. The Related Art
Pipelines are widely applied in transportation of petroleum, chemicals, natural gas, etc. and are indispensable. With the development of pipeline industry, pipeline robots are gradually applied to cleaning of pipelines, detection of defects, etc. Accurate positioning of pipeline robots is essential for the robots to complete work. The pipeline robot positioning technique is a technique to position pipeline robots in pipelines. Many methods are used for positioning pipeline robots, and GPS navigation positioning, CCD visual positioning and photoelectric coded disk positioning are widely applied at present.
GPS navigation positioning is a technique that a satellite continuously sends ephemeris parameters and time information of the satellite, and then, the user determines the three-dimensional position, the three-dimensional direction, the moving speed and the time information of the receiver through calculation after receiving the information. GPS can position pipeline robots. However, submarine pipelines are really long and are deeply buried, and the surrounding environment is adverse, so GPS can hardly accomplish navigation positioning.
The charge coupled device (CCD) which is made of photosensitive semiconductor materials can convert light to charges and then to digital signals through the A/D converter chip. After compressed, the digital signals are stored in the flash memory or the built-in hard disk card in the camera, so data can be easily transmitted to computers. However, pipelines have a lot of oil contaminants, so the CCD visual positioning cannot obtain effective visual features.
The photoelectric coded disk is made of optical glass and is engraved with many concentric yards, and each yard has transparent parts and nontransparent parts arranged regularly. In operation, light is projected onto the photoelectric coded disk, and the photoelectric coded disk rotates with the moving object. After passing through the slit, the light penetrating through the bright zone is received by photosensitive elements, wherein the photosensitive elements are arranged correspondingly with the yards. When the photoelectric coded disk rotates in different positions, the combination of output signals from the photosensitive elements shows digital quantity of a certain rule which represents the angular displacement of the axis of the photoelectric coded disk. According to the angular displacement and the diameter of the photoelectric coded disk, the moving distance of the photoelectric coded disk can be calculated to position the pipeline robots. However, oil contaminants in the pipelines also have effects on the photoelectric coded disk, and the photoelectric coded disk cannot position the pipeline robots due to turbulence and slip.